Resilient bulb seals, lip type seals and trims are generally known and are commonly used for automobile window, trunk, and/or door sealing and trimming and are often placed along the abutting edges of parts. Another one of such applications is found in the field of mobile living quarters having extendable or slide-out rooms for providing a seal between the body panel of the recreational vehicle and the extendable room frame. A bulb seal is commonly placed along the interface between the abutting surfaces of parts to prevent water, debris, and excessive air drafts from entering the interior of the automobile and/or mobile living quarters from the outside. This seal often includes at least two sub-parts; a bulb portion and a structural member, each generally extending along a side of an opening of the motor vehicle. The structural member comprising a mounting portion is typically placed along the edge of the motor vehicle part to mount the seal to the part, and the bulb portion extends therefrom to form a resilient seal between the abutting edges of the motor vehicle parts around the outside edge of the opening. Optionally, at least one flange seal can additionally be used adjacent the opening so as to provide contact for additional interface between various surfaces of parts to prevent water, debris, and excessive air drafts from entering, e.g., placed along the edge of the sidewall and flexibly protrudes against the adjacent sidewall of the slide-out room so as to be in constant contact with the sidewall at all positions of the room between its open and closed positions.
Generally, using materials with different durometers is desirable for providing the respective mounting and sealing functions. Typically, the mounting portion has a greater stiffness and higher durometer than the bulb portion for installation and providing structural strength to help prevent the bulb seal from disengaging from the part edge and falling off.
Bulb seals and lip type seals are conventionally made by a co-extrusion process where the mounting portion and bulb portion are co-extruded forming an extruded strip of continuous length. This extruded strip is then delivered to a bath or trough containing cooled water to cool the extrusion. After passing through the bath the strip is usually trimmed and then cut into a desired length to form the finished bulb seal. One of the problems with this type of conventional process for making bulb seals is that due to the different durometers and the pre-cut length of continuous extruded material the mounting portion and bulb portion have different cooling rates. The continuous pre-cut extrusion strip prevents the cool water from entering the inside length of the bulb since there is no open end until after the seals are cut to their desired length after exiting the trough, thus, the bulb portion cannot additionally be effectively cooled from the inside. However, the mounting portion typically not only has a different material and higher durometer with a different cooling rate than the bulb portion, but also, unlike the bulb portion, does allow the cool water to enter the inside mounting portion due to its typical C or U-like shape. The resultant cooling differentials adversely affect part dimensions, tolerances, part integrity, and other material and structural properties of the finished bulb seal. Any other portions having different durometers and shapes also have resultant cooling differentials. Another typical problem caused by the differential cooling and deficient conventional processing is that the legs or walls of the mounting portion become curved, wavy, scratched, and/or otherwise compromised. Typical co-extrusion dies and processing steps have attempted unsuccessfully to overcompensate for the problem of uneven cooling and/or cooling cycle time variations additionally causing further processing issues, complexity, perpetual adjustments, e.g., equipment speed adjustment, and additional costs.
Therefore, it is desirable to have a method for making various types of multiple durometer seals, that helps to avoid or overcome the disparity in the cooling expansion and cooling differential between the multiple durometers. It is also desirable to have improved quality multiple durometer seals, without adversely affecting or compromising their rigid carriers or mounting portion and tolerances.